My system only uses two wires (Rh and W1), so the battery only gets powered when heating is activated. If I turn the system to away and the heat doesn't come on for days or weeks at a time, who long till the battery is depleted.

I understand the wifi will be turned off after the battery gets below a certain point. Will I have to set up my heating schedule to turn on for a period every so many days to keep the battery charged and so that I can turn on the heat via wifi before I come back to the house after weeks of abscence? If so, how long should it take to charge the battery?